Where did the immigrants from Anxi in the Tang Dynasty go? After the fall of Anxi four towns,

After the Anshi Rebellion, most of the troops in Anxi, Beiting, Hexi and Longyou were transferred, and Tubo successively occupied Longyou and Hexi States, and the passage between Anxi four towns and the court was interrupted. But the rest of the four towns still stick to the towns. In the second year of Tang Dezong Jianzhong (78 1), Guo Xin, who stayed in the four towns, arrived in Chang 'an. The court appointed Guo Xin as the general manager of Anxi, lord protector, and the ambassador of our four towns, and ordered the soldiers of the four towns to move to Qidu to reward their efforts in sticking to the four towns. In the fifth year of Zhenyuan (789), Wukong returned to China from China and passed through Shule town to meet with the garrison commander Yang Lu. To khotan town, see guarding Zheng according to; When I arrived in Qiuci, I met Guo Xin, ambassadors of four towns and representatives of Anxi. When I arrived in Yanqi Town, I met Yang Riyou, the garrison commander, and said that the four towns of Anxi were still guarded by the Tang Dynasty. In the sixth year of Zhenyuan (790), Tubo occupied Beiting (except Xizhou in Beiting, in 792 AD, Tubo occupied Xizhou and completely occupied Beiting) and occupied Khotan, one of the four towns in Anxi. In the following years, Tubo occupied three other towns in Anxi. At present, there is no data to explain the exact time when Tubo began to occupy the other three towns in Anxi. The fierce competition between post-experience and Uighur. In the middle of the 9th century, four towns appeared in the north and south of Tianshan Mountain and in Anxi.